In an attempt to reduce hydrocarbon emissions, environmental regulations in certain areas of the country require that fuel vapors are to be recovered in order to prevent their escape into the atmosphere. One means of complying with these regulations is the use of fuel nozzle assemblies incorporating vapor-recovery systems of the type described in U.S. Pat. No. 4,060,110 (Bower). Vapor-recovery fuel dispensing nozzles of this type generally include a flexible vapor-recovery shroud positioned around the nozzle discharge spout, a faceplate connected at the outer end of the shroud, and spring means located in the shroud and arranged around the discharge spout so that the faceplate is forced to sealingly engage the fuel tank fillpipe when the discharge spout is inserted therein during refueling. As fuel is pumped into the fuel tank, fuel vapors flow out of the tank and by way of the shroud to a vapor-receiving passage formed in the nozzle main body portion. From the vapor-receiving passage, the refueling vapor emissions flow through a vapor return line to a hydrocarbon storage tank at the service station where they are stored pending their removal. To operate effectively, these vapor-recovery fuel dispensing nozzles are also provided with some type of vapor seal valve or control system to prevent vapors in the storage tank from being displaced into the atmosphere through the shroud when the nozzle is not in use; additionally, these nozzles will normally include a no-seal, no-flow interlock which prevents the nozzle from operating until its faceplate seals against the fillpipe.
An alternate to the above-described vapor-recovery system which eliminates the necessity of using a service station vapor-recovery fuel dispensing nozzle is an on-board system for controlling refueling vapor emissions. Basically, this system, which is described in API Publication No. 4306, "On-Board Control of Vehicle Refueling Emissions--Demonstration of Feasibility", October 1978, is a modified version of current automobile evaporative control systems in which hydrocarbons are absorbed by activated charcoal contained in a carbon canister located on the vehicle. In the on-board control system, a sealing means is provided in the fillpipe to form a vapor-tight seal around the nozzle discharge spout so that refueling vapors will flow from the fuel tank to the vehicle's carbon canister where they are absorbed and subsequently purged to flow to the engine's carburetor or intake manifold. Studies of various seal types to be used in the fillpipe at the discharge spout/fillpipe interface, see API Publication No. 4306, part entitled "Report on Nozzle/Fillpipe Interface Development", have shown that a 99+% effective seal may be made around the discharge spout at its interface with the fillpipe. This may be compared to the 90-95% effective seal made with the vapor-recovery fuel dispensing nozzles of the type described above wherein the nozzle faceplate seals against the fillpipe.
Cost comparisions of the two above-discussed vapor-recovery systems have shown that their individual, overall costs are approximately the same, see API Publication No. 4306, part entitled "Cost Comparison for Stage II and On-Board Control of Refueling Emissions", wherein with the service station vapor-recovery fuel dispensing nozzle, the cost is essentially borne by the gasoline retailers in that they must buy and install the vapor-recovery fuel dispensing nozzle system, while with the on-board vapor control system, it is the automobile manufacturer who must bear the economic burden of complying with vapor control regulations. To distribute the costs of recovering refueling emissions between the automobile manufacturers and gasoline retailers, a vapor-recovery system could be designed to use a vapor-recovery nozzle that is less complex and costly than that of the type described in U.S. Pat. No. 4,060,110 in which the nozzle is to be sealingly engaged at the fillpipe interface by a sealing means that is manufactured as a part of and located in the fuel tank fillpipe.
A design proposed heretofore for a vapor-recovery system which can be said to be directed to this idea of distributing cost between automobile manufacturers and gasoline retailers is shown in API Publication No. 4222, "Vehicle Refueling Emissions Seminar", page 12, "An Automobile Industry Viewpoint", December 1973. The vapor-recovery system shown in this report includes a concentric spout extending a short distance from the main body of the fuel nozzle and arranged around the nozzle discharge spout to be sealingly engaged by a tight fillpipe connection of some sort at the opening of the fillpipe such that refueling emissions will flow out of the fuel tank by way of the concentric spout. This system, however, is not really a workable concept in that it lacks several important qualifications necessary for effective operation in meeting the requirements of current vapor emission regulations. First, the cross-sectional area of the vapor-recovery chamber formed by the concentric spout is too small to receive substantially all the vapors that will be produced during a typical refueling; this is a problem because the vapors which are not recovered will drive the pressure up in the fuel tank which will cause the seal made at the concentric spout to leak, and in extreme cases, it may even cause the fuel tank to buckle. Therefore, this system lacks the basic requirement that all vapor-recovery systems must possess in that it does not provide a vapor-tight seal at the discharge spout/fillpipe interface to minimize the escape of hydrocarbons into the atmosphere. Second, the system disclosed in API Publication 4222 does not have a vapor seal valve or some type of control system for preventing recovered vapors in the storage tanks from being displaced into the atmosphere through the vapor-receiving apparatus, the concentric spout, when the nozzle is not in use. Finally, this system does not have a no-seal, no-flow interlock which prevents the nozzle from operating until a seal is made at the discharge spout/fillpipe interface.
Accordingly, the coaxial vapor-recovery nozzle of the present invention, which includes a vapor seal valve and a no-seal, no-flow interlock, provides a workable vapor-recovery system which distributes the cost of recovering refueling emissions between the automobile manufacturers and the gasoline retailers while at the same time providing a system which provides a virtually vapor-tight seal, approximately 99+%, at the discharge spout/fillpipe interface. The present invention also offers the advantage of reducing the over-all complexity of the vapor-recovery fuel dispensing nozzle by doing away with the flexible vapor-recovery shroud, the faceplate, and the various spring means used on most commercially available vapor-recovery fuel dispensing nozzles; this has the effect of reducing the cost of the nozzles and the breakdown problems associated with their use. The present invention also eliminates the need for using an on-board carbon canister system and thus the problems and costs associated with its development into a commercially viable system.